Ozonated water flow and concentration control apparatus

ABSTRACT

The invention features an apparatus and a method for supplying ozonated water to more than one process tool. Ozonated water of a first concentration received from an ozonated water generator and water received from a source are mixed to produce ozonated water of a second concentration. The ozonated water of a second concentration is supplied to a first process tool. Ozonated water from the ozonated water generator is supplied to a second process tool while supplying the ozonated water of the second concentration to the first process tool.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 09/653,506, filed Sep. 1, 2000, now abandoned theentire disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The invention relates generally to manufacturing of semiconductordevices and more particularly to the control of ozonated deionized watersupplied to semiconductor processing tools.

BACKGROUND OF THE INVENTION

Use of ozonated deionized water in semiconductor manufacturing canprovide relatively simple, safe processing steps, such as wafer surfacecleaning, passivation, native oxide removal, and removal of photoresist.

Ozonated deionized water generators generally produced ozonated waterthrough use of contactors that permit diffusion of ozone from a gas intodeionized water. Membrane contactors use an ozone permeable membrane toprovide physical separation between liquid and gas, while packed columncontactors provide intimate mixing of liquid and gas, under pressure toenable higher ozone concentrations.

A semiconductor fabrication facility often has multiple tools thatrequire ozonated water. Different tools can require different ozoneconcentrations and flow rates. The purchase, operation and maintenanceof multiple ozonated water generators can increase manufacturing costsand line shut-downs.

It would be beneficial to have a less expensive, more reliable, moreflexible and more rapidly responsive ozonated water source.

SUMMARY OF THE INVENTION

The present invention relates to an ozonated water control unit for usein an improved ozonated water supply system. The control unit can modifythe flow rate and/or concentration of ozonated water received from anozonated water generator, for subsequent delivery to a process tool. Oneor more control units can be used with a single generator to supply morethan one tool with individualized ozonated water needs.

In various embodiments, the ozonated water supply system cansimultaneously supply ozonated water of different ozone concentrationsto different process tools, even if the system includes only oneozonated water generator. Use of one or more control units with as fewas one ozonated water generator permits independent control of ozonatedwater supplied to two or more process tools.

Each control unit controls its output flow rate and/or concentration ofozonated water. Thus, the parameters of the supplied ozonated water canbe tailored for each process tool. In one embodiment, the system cansupply low ozone concentration ozonated deionized water, for example,for a cleaning process, and simultaneously supply higher ozoneconcentration ozonated deionized water, for example, for a strippingprocess.

Thus, in a first aspect, the invention features a method of supplyingozonated water to more than one process tool. Ozonated water of a firstconcentration received from an ozonated water generator and waterreceived from a source are mixed to produce ozonated water of a secondconcentration. Ozonated water of the second concentration is supplied toa first process tool, and ozonated water from the ozonated watergenerator is supplied to a second process tool.

In a second aspect, the invention features another method of supplyingozonated water to more than one process tool. The method includesproviding an ozonated water control unit. The ozonated water controlunit includes an ozonated water input line for receiving ozonated waterof a first concentration from an ozonated water generator and a waterinput line for receiving water from a source. The unit also includes anozonated water output line in fluid communication with the ozonatedwater input line and the water input line. A valve controls a flow rateof water in the water input line to produce ozonated water of a secondconcentration in the output line, in cooperation with a flow rate ofozonated water in the ozonated water input line.

The method further includes supplying ozonated water of the secondconcentration from the output line to a first process tool and supplyingozonated water from the ozonated water generator to a second processtool.

In a third aspect, the invention features an ozonated water controlunit. The control unit includes an ozonated water input line forreceiving ozonated water from an ozonated water generator, a water inputline for receiving water from a source and an ozonated water output linein fluid communication with the ozonated water input line and the waterinput line. The unit also includes a valve for controlling a flow rateof water in the water input line to produce ozonated water of a secondconcentration in the output line, in cooperation with a flow rate ofozonated water in the ozonated water input line.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, in accordance with preferred and exemplary embodiments,together with further advantages thereof, is more particularly describedin the following detailed description, taken in conjunction with theaccompanying drawings.

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating principles of the invention.

FIG. 1 is a block diagram of an embodiment of the relationship betweenan ozonated water generator and other components utilized insemiconductor manufacturing.

FIG. 2 is a block diagram of an embodiment of an ozonated watergenerator.

FIG. 3 is a block diagram of an embodiment of an ozone generator module.

FIG. 4 is a block diagram of an embodiment of a contactor modulecomprising a membrane contactor.

FIG. 5 is a block diagram of an embodiment of a contactor modulecomprising a packed column contactor.

FIG. 6 is a block diagram of an embodiment of a contactor modulecomprising more than one contactor.

FIG. 7 is a block diagram of an embodiment of a portion of a contactormodule.

FIG. 8 is a block diagram of an embodiment of a portion of a contactormodule.

FIG. 9 is a cross-section of an embodiment of a packed column contactor.

FIG. 10 is a block diagram of an embodiment of an ozone destructionmodule.

FIG. 11 is a graph of ozone concentration versus time in ozonateddeionized water output from a contactor.

FIG. 12 is a block diagram of an embodiment of a contactor.

FIG. 13a is a prior art wet bath.

FIG. 13b is an embodiment of a wet bath system comprising the contactorof FIG. 12.

FIG. 14 is block diagram of an embodiment of an ozonated water controlunit.

FIG. 15 is a block diagram of an embodiment of multiple ozonated watercontrol units, an ozonated water generator, a pure water source andthree process tools.

FIG. 16 is a block diagram of an embodiment of an ozonated watergenerator and a control unit delivering ozonated water to two processtools.

FIG. 17 is a detailed block diagram of an embodiment of a ozonated watercontrol unit.

DETAILED DESCRIPTION

In highly simplified form, FIG. 1 shows an embodiment of an ozonatedwater generator 1000 in physical relationship to other componentsutilized in semiconductor manufacturing. The ozonated water generator1000 receives deionized water (“DI water”) for a DI water supply 20,oxygen (“O2”) from an oxygen gas supply 30, and supplies ozonateddeionized water (“DIO3”) to one or more semiconductor process tools 40.Used or excess DI water or DIO3 can be dumped via drain lines 50. In oneaspect, the invention provides an ozonated water generator with improvedcontrol, lower cost, and improved reliability.

In a more detailed embodiment, the block diagram of FIG. 2 depictsrepresentative modules of the ozonated water generator 10 and relatedcomponents contained within a cabinet 1020. For clarity, electrical andair pressure control components of the ozonated water generator 10 arenot shown.

An ozone (“O3”) generator module 800 generates O3 from oxygen deliveredby a O2 line 813. A carbon dioxide (“CO2”) line supplies CO2 for use bythe module 800. Cooling water is supplied to the O3 generator module 800by a cooling water input line 812 and removed via a cooling water outletline 811. The O3 generator produces O3, typically mixed with CO2 and O2.Some O2 remains since the conversion to O3 is less than 100% efficientwhile CO2 is optionally added depending on user needs. This dry gasmixture is delivered to a contactor module 100 via a dry gas line 815.

The contactor module 100 produces DIO3 from DI water supplied via a DIwater line 112 and O3 received via the dry gas line 815. The DIO3generally comprises DI water and O3, O2, and CO2 dissolved in the DIwater. The DIO3 is directed toward the semiconductor tools 40 via a DIO3line 115.

As will be discussed below with reference to FIGS. 4, 5, and 6, invarious embodiments of the contactor module 100, the contactor module100 comprises one or more contractors 110, 120 of varying type. The useof a O3/CO2 gas mixture is optional in the DIO3 generation process,serving in part to stabilize the concentration of O3 in ozonated DIwater.

A pressure relief drain line 113 carries water emitted by the contactormodule 100 in response to excessive water pressure (described in detailbelow). Water from the pressure relief drain line 113 is deposited intoa drip pan 1040. The drip pan 1040 is also positioned to capture waterleaks from the contact module. Liquid may be removed from the drip pan1040 via a cabinet drain 1045.

A water dump line 114 carries excess DI water or DIO3 to a drainexternal to the ozonated water generator 1000. Used DIO3 water from thesemiconductor tools 40 can be returned to the ozonated water generator1000 via a DIO3 return line 41, a flow meter 11 and a flow rate controlvalve 12. This permits the ozonated water generator 1000 to providecomplete monitoring and control of the use of DIO3 by the semiconductortools 40.

The contactor module 100 typically produces a humid gas comprising O2,H2O, O3, and CO2 as an exhaust product of the production of DIO3. Thehumid gas is directed along the humid gas line 911 to the ozonedestruction module 900. The destruction module 900 substantiallyeliminates ozone from the humid gas prior to exhaust of the humid gasalong gas exhaust line 912. This process protects the environment andsemiconductor processing workers from the potentially harmful presenceof ozone. As an additional safety precaution, the cabinet 1020 isequipped with a gas leak detector 1030, i.e. a cabinet “sniffer”, tomonitor for ozone gas leaks within the cabinet 1020.

For simplicity in the following descriptions, controlling and monitoringelements related to gas and liquid lines are given common numericalidentifiers in FIGS. 3-10. These control and monitoring elementsinclude: volume flow rate meters 11; volume flow rate control valves 12;on/off valves 13; pressure regulators 14; filters 15 (for particulatesor condensate); check valves 16; pressure relief valves 17; samplevalves 18; flow rate restrictors 19; ozone concentration monitors 20;condensation monitors 21; and temperature gauges 22. These elements areillustrative and not comprehensive. Control and monitoring elements areshown in the Figures primarily for illustrative purposes. The number,type and placement of such elements can be varied with the needs ofdifferent embodiments.

It should further be understood that gas and liquid lines areconstructed of appropriately selected materials. Dry gas lines and DIwater lines can be comprised of stainless steel. Lines carrying liquidor humid gas that contains ozone are typically comprised of afluoropolymer.

FIG. 3 shows a block diagram of an embodiment of the ozone generatormodule 800 in greater detail. An ozone generator 810 receives oxygenfrom the O2 line 813 via an on/off valve 13 and a pressure regulator 14and converts the O2 into O3. CO2 can also be delivered to the ozonegenerator 810 via the CO2 gas line 814, pressure regulator 14, volumeflow rate control valve 12 and flow rate restrictor 19. Further, CO2 canbe added to gas after it exits the ozone generator 810 via volume flowrate control valve 12 and check valve 16. The check valve 16 blocksback-flow of gas into the CO2 delivery lines.

In one embodiment, the ozone generator 810 utilizes a dielectric barrierdischarge to produce dry ozone. The ozone concentration depends on thevolume flow rate through the discharge as well as the power, pressureand temperature of the discharge.

Addition of CO2 to the O2 prior to entry into the ozone generator 810provides a dopant for the O3 creation process. It protects against longterm deterioration of performance of the ozone generator 810 due tooxidation of a power electrode. Alternative dopants can be used, such asN2 or CO. Additional CO2 can be added to the dry gas that exits theozone generator 810. CO2 has the additional advantage of stabilizing O3concentrations.

Use of CO2 has other advantages. Use of N2 creates the risk of nitricoxide formation during discharge. This can lead to chromium contaminantseven in the presence of electropolished stainless steel tubes.

Large amounts of CO2 are required for stabilization of ozone in DIO3.The half-life governing the decay of ozone is a function of the qualityof the DI water. Preferably, this quality should provide a half-life ofabout 15 minutes. N2, too, can affect stability of ozone, along with thepresence of CO2. While high purity CO2 and O2 are preferred, as analternative, low purity O2, with inherent N2 contamination, can be used,taking advantage of the N2 impurity as a dopant. Typically, N2 of about50 to 100 ppm or CO2 of about 100 to 500 ppm is required forstabilization. CO2, however, is typically required for enhancement ofshort-term stability. Hence, CO2 is typically added to the gas bothbefore and after entry into the ozone generator 810.

The resulting dry gas can be sampled via sample valve 18, to determinethe concentrations of O3, O2 and CO2. The dry gas then passes to the drygas line 815 via filter 15, volume flow rate control valve 12, checkvalve 16, filter 15, and on/off valve 13.

The ozone generator module 800 is also provided with cooling water viathe cooling water input line 812 and the cooling water output line 811.The cooling water is delivered to the ozone generator 810 via on/offvalve 13, filter 15, volume flow rate control valve 12 and volume flowrate meter 11. After exiting the ozone generator, the cooling waterpasses through on/off valve 13.

FIGS. 4 through 8 show various embodiments of the contactor module 100.The contactor module 100 generally includes one or more contactors ofvarious types. For example, different types of counter-currentcontactors can advantageously be employed. In counter-currentcontactors, gas and water move in opposite directions through thecontactor.

Contactors of the counter-current type have further variants. Membranecontactors utilize a hydrophobic membrane to separate gas and liquidwithin the contactor. Typically, dry gas enters the top of the membranecontactor and exits the bottom, while DI water enters at the bottom andDIO3 exits at the top. Packed contactors in contrast utilize directcontact between gas and liquid, with a packing material used to slowtransit through the contactor. Typically, DI water enters at the topwhile the dry gas enters at the bottom. The packing material increasesthe duration of contact between gas and liquid. The packing material cancomprise, for example, fluoropolymer, quartz, or sapphire.

Since gas and liquid are separated by a membrane in a membranecontactor, pressure differences between the gas and the liquid canexist. Further, the inlet DI water volume flow rate is coupled to theoutlet DIO3 volume flow rate. Conversely, liquid and gas pressures areequal in packed column contactors and the inlet and outlet volume flowrates are decoupled. Hence, for short periods, the inlet and outletvolume flow rates can differ. In part due to these differences, membranecontactors have a relatively low maximum volume flow rate though goodcontrollability, while packed column contactors typically have a greatermaximum volume flow rate though with poorer controllability.

During interaction of liquid and gas, ozone in the gas dissolves in theliquid. Generally, the ozone concentration in the liquid, atequilibrium, will be proportional to the partial pressure of ozone inthe gas. In the case of a packed contactor, for example, the contactortypically operates under pressure to provide the potential for higherozone concentration DIO3 output. Time of contact between liquid and gaswill also affect the ozone concentration in liquid exiting thecontactor. For a one yard tall packed contactor, typical duration ofliquid passage through the contactor is about 5 to 10 seconds.

As shown in FIG. 4, the contactor module comprises a membrane contactor110. The lower portion of the contactor 110 receives DI water from theDI water line 112 via volume flow rate control valve 12. In the event ofexcess inlet water pressure, a pressure relief valve 17 can release aportion of DI water to the pressure relief drain line 113. Afterprocessing within the contractor 110, the DIO3 leaves the upper portionof the contactor 110 via a volume flow rate meter 11 and is directed tothe DIO3 line 115 via an on/off valve 13.

Excess or unneeded DIO3 exiting the contactor 110 can be directed to thewater dump line 114 via an ozone monitor 20, an on/off valve 13, avolume flow rate meter 11, and a volume flow rate control valve 12.

The upper portion of the contactor 110 receives the ozone containing drygas from the dry gas line 815 via an on/off valve 13. Humid gas existsthe lower portion of the contactor 110 and is directed to the humid gasline 911 via a volume flow rate meter 11. Subsequently, the ozonedestruction module 900 removes ozone from the humid gas.

FIG. 10 shows an embodiment of the ozone destruction module 900 in moredetail. An ozone destructor 910 receives humid gas from the humid gasline via a volume flow rate control valve 12, an on/off valve 13, afilter 15 and a condensate monitor 21. The humid gas can be sampled viaa sample valve 18.

The ozone destructor 910 reduces ozone concentration in the humid gasvia use of a catalyst. Exhaust gas from the ozone destructor 910 isdirected to the exhaust gas line 912 via a temperature gauge 22 and avolume flow rate monitor 11. Generally, the efficiency of ozonedestruction is assumed to be adequate as long as the temperature,monitored via the temperature gauge 22, remains above a minimum level.

FIG. 5 shows another detailed embodiment of the contactor module 1001.In this embodiment, the contactor module 100 comprises a contactor 120of the packed column type. The upper portion of the contactor 120receives DI water from the DI water line 112 via volume flow ratecontrol valve 12. After processing within the contractor 120, the DIO3leaves the lower portion of the contactor 120 via a volume flow ratemeter 11 and is directed to the DIO3 line 115 via an on/off valve 13.

Excess or unneeded DIO3 exiting the contactor 120 can be directed to thewater dump line 114 via an ozone monitor 20, an on/off valve 13, avolume flow rate meter 11, and a volume flow rate control valve 12. Inthe event of excess water pressure within the contactor 120, a pressurerelief valve 17 can release a portion of water residing in the lowerportion of the contactor 120 to the pressure relief drain line 113.

The lower portion of the contactor 10 receives the ozone containing drygas from the dry gas line 815 via an on/off valve 13. Humid gas exitsthe upper portion of the contactor 120 and is directed to the humid gasline 911 via a volume flow rate meter 11. Subsequently, the ozonedestruction module 900 removes ozone from the humid gas.

The embodiment depicted in FIG. 5 further provides for monitoring ofliquid level in the contactor 120 through a liquid level sensor 150 thatis in fluid communication with the contactor 120. Liquid level ismeasured via a capacitive gauge 152. Further, if the liquid level dropsbelow a lowest permissible level, as sensed via a light barrier 153, theon/off valve 13 is closed to prevent further removal of liquid. If thelevel rises above a highest permissible level, as sensed by anotherlight barrier 151, another on/off valve (not shown) is closed to preventfurther entry of DI water into the contactor 120. In either case, analarm is given as notice of the problem condition.

FIG. 6 shows an embodiment of a contactor module 100 that employs twocontactors 120 operating in parallel. For clarity, components of theembodiment of FIG. 6 that are comparable to those in FIG. 5 are notshown. Use of two or more contactors 120 in parallel has severaladvantages, including larger possible flow rates of DIO3 and continuedproduction of DIO3 in the event that one of the contactors 120 fails.Further manufacturing and operation of two relatively small contactors120 can be less costly than a single relatively large contactor 120. Inanother embodiment, two or more contactors 120 are operated in series toprovide higher possible ozone concentrations in the DIO3.

FIG. 7 shows a portion of a further embodiment of a contactor module 100that is related, in part, to the embodiment of FIG. 5. For clarity,components of the embodiment of FIG. 7 that are comparable to those inFIG. 5 are not shown. The embodiment is shown with a packed columncontactor 120, however, a variety of contactor types can be employed inconjunction with the principles utilized in this embodiment.

A portion of DI water received from the DI water line 112 is diverted bya DI water bypass line 610. Alternatively, a second DI water line (notshown) could supply the DI water bypass line 610.

After passing a volume flow rate meter and a volume flow rate controlvalve, DI water in the DI water bypass line 610 is mixed with DIO3exiting the contactor 120. DIO3 derived from this mixture is directedtowards the semiconductor tools via the DIO3 supply line 115. Byadjusting the flow rate of DI water in the bypass line 610, the ozoneconcentration and flow rate of DIO3 in the DIO3 line can be varied.

A number of advantages arise from the use of the bypass line 610.Typically, prior art ozonated water generators produce ozoneconcentration transients in DIO3 when implementing a demand for a changein concentration. Changing the flow rate of DI water or dry gas enteringa contactor to change ozone concentration leads to a period of timeduring which conditions within the contactor transition to a newsteady-state. This effect is illustrated by the graph shown in FIG. 11.

For example, by decreasing the flow rate of DIO3 exiting a contactor,the concentration of ozone in the DIO3 can be increased. Decreasing theflow rate can be used to increase time span that water spends within thecontactor 110, 120. This permits greater duration of interaction betweenthe water and ozone within the gas. There is a time delay, however,during which DIO3 exiting the contactor has not spent the full,increased time span within the contactor. Hence, the ozone in exitingDIO3 gradually increases to the new, desired level. Further, ringing oroscillations in concentration, as illustrated qualitatively in FIG. 11,can be superimposed on the gradually increasing ozone concentration.

These effects are generally undesirable in semiconductor processing.Users of DIO3 often wish to make immediate, stable adjustments inconcentration level. By adjusting the flow rate of DI water in thebypass line 610, relatively immediate and stable changes in ozoneconcentration in DIO3 delivered to the DIO3 line 115 can be achieved.Excess DIO3 beyond that required by the semiconductor tools 40 can bedirected to the water dump line 114.

Using the above approach, a constant flow rate of water in the contactor110, 120 can be maintained to maintain a stable ozone concentration inDIO3 exiting the contactor 110, 120. This very stable supply of DIO3 canthen mixed with DI water of a variable flow rate to achieve desiredchanges in concentration in DIO3 delivered to the DIO3 line 114. In arelated embodiment, a constant, low flow rate of water is maintained inthe contactor 110, 120 at all times, even when DIO3 demand from thesemiconductor tools is zero. With a constant flow, DIO3 is nearlyimmediately available. Further, with a relatively low flow rate in thecontactor, relatively little volume flow of DIO3 need be dumped when noDIO3 is needed. At these times, DI water flowing through the bypass line610 can be reduced or shut off to further conserve water.

As an example of the above method, the contactor 120 can be operated ata constant flow rate of 5 l/min (liters per minute) with an exit DIO3ozone concentration of 80 ppm. Mixing a 15 l/min flow rate of DI waterfrom the bypass line 610 with this contactor 120 output will yield DIO3of 20 ppm at a flow rate of 20 l/min in the DIO3 line 114. The full 20l/min of DIO3 at 20 ppm concentration can be utilized by thesemiconductor tools 40, or a portion can be dumped.

Further benefits can accrue through use of the above method. As oneexample, maintaining water flow in the contactor 110, 120 or in thebypass line 610 can reduce bacterial growth. For example, DI water flowcan be maintained in the bypass line 610 to provide continuous flow inthe bypass line 610 and other DI water carrying lines to protect theselines against bacterial growth. As another example, changes in liquidflow rates through a contactor 110, 120 can cause pressure spikesleading to failure of the contactor 110, 120. Use of the above method toreduce or eliminate these flow rate changes can thus increase contactor110, 120 reliability.

FIG. 8 shows a portion of a further embodiment of a contactor module 100that is related, in part, to the embodiment of FIG. 5. For clarity,components of the embodiment of FIG. 8 that are comparable to those inFIG. 5 are not shown. The embodiment is shown with a packed columncontactor 120, however, a variety of contactor types can be employed inconjunction with the principles utilized in this embodiment.

After exiting the contactor 120 and passing a volume flow rate meter, aportion of DIO3 can be diverted via a recirculation line 180 to againenter the contactor 120, optionally via a reservoir 710. Though notshown, a water pump can be included to urge the DIO3 towards thecontactor 120. The reservoir, in part, provides buffering, i.e. storage,of diverted DIO3 to permit greater control over recirculation ofdiverted DIO3.

The diverted DIO3 can reenter the contactor 120 via a liquid lineconnector used for DI water received from the DI water line 112.Alternatively, the contactor 120 can include a separate connector forthe diverted DIO3 to reenter the contactor 120.

With recirculation of diverted DIO3 through the contactor, DIO3 ofincreased ozone concentration can be obtained. This provides advantagesover prior art ozonated water generators. For example, higher ozoneconcentration DIO3 can be produced in comparison to prior generatorsthat incorporate a comparable contactor. Further, a smaller, lessexpensive contactor can be employed to produce DIO3 of a desired ozoneconcentration level.

With reference to the cross-sectional view of FIG. 9, an improved packedcolumn contactor 500 is now described. The contactor 500 can beadvantageously employed in various embodiments of the contactor module100, such as those described above.

The contactor 500 comprises a liquid and gas interaction vessel withinwhich elevated pressures are maintained during operation of thecontactor 500. The vessel comprises a first end portion 510 and a secondend portion 520. As shown in FIG. 9, the vessel further comprises acentral portion 530. The first end portion 510 is joined to a first endof the central portion 530 while the second end portion 520 is joined toa second end of the central portion 530, to provide a substantiallyliquid and gas tight liquid and gas interaction vessel. Within thevessel are packing restraints 560 and packing material (not shown).

The portions 510, 520, 530 are preferably formed from a polymer thatcomprises a fluoropolymer. The fluoropolymer is selected from a groupcomprising pertetrafluoroethylene, perfluoroalcoxy, polyvinlydifluoride,and fluoroethylenepropylene. Generally, materials with ozone resistancecan be considered for use in forming the portions 510, 520, 530. Theportions 510, 520, 530 can be manufactured by various means. Forexample, some fluoropolymers, such as perfluoroalcoxy, are amenable toinjection molding. Other, such as pertetrafluoroethylene, can bemachined.

A sufficient wall thickness of the portions 510, 520, 530 is chosen toprovide self-supporting mechanical stability during pressurizedoperation of the contactor. Hence, unlike prior art packed columncontactors, the contactor 500 requires no stainless steel housing.

Assuming a cylindrical shaped vessel, a sufficient wall thickness can becalculated through use of the following equations:

t=r(P/σ_(max));

σ_(max)=(1/s)σ_(y);

where t is the required wall thickness, r is the internal radius of thevessel, P is the internal pressure, σ_(max) is the maximum allowabletensile wall stress, σ_(y) is the yield strength for the particularmaterial used to form the vessel portions, and s is the safety factor.Using a greater safety factor with a particular vessel material, i.e. aparticular maximum allowable tensile wall stress, will lead to a greaterthickness t for a given operating pressure P.

For example, for an operating pressure of 0.75 MPa (million pascals),i.e. about 7.5 atmospheres, an internal radius of 3 inches, a safetyfactor of 2, and vessel portions 510, 520, 530 comprisingperfluoroalcoxy with a yield strength of 15 MPa, the calculated requiredwall thickness is 0.3 inch. Use of a smaller safety factor, for exampleabout 1, would allow use of a thickness of about 0.15 inch. Where a moreconservative design is desired, a safety factor of 4, for example, wouldgive a required thickness of 0.6″. Greater thicknesses can be used, forexample 1.2 inches or more, however this can add to the cost and weightof the contactor 500.

Alternatively, the thickness of vessel portions can be derivedempirically, by manufacturing vessels of varying thickness andsubjecting these samples to varying test pressures to determine failurepressure. In some embodiments, the thickness varies at different siteson the vessel. For example, thicker end portions 510, 520 can be used toprovide more stability for gas or liquid line attachments to thecontactor 500.

Pressure tightness and stability at the joints between the portions 510,520, 530 can be assisted via use of, for example, gaskets 540 and clamps550 (clamps are indicated only on one side of the vessel in the crosssection of FIG. 9).

The contactor 500 has several advantages over prior packed columncontactors. The stainless steel housing of prior contactors leads to arelatively very heavy and expensive contactor, generally requiring topand bottom steel flanges. Such prior contactors typically incorporate adifficult to manufacture polytetrafluoroethylene liner. In contrast, thecontactor 500 requires few parts, all of which can be produced viarelatively inexpensive injection molding techniques. This can provide apacked column contactor 500 that is more reliable than prior packedcolumn contactors at a cost about 80% less than prior packed columncontactors. Further, via injection molding, liquid or gas lineconnectors 511, 512, 513, 514 can be formed as integral portions of thefirst end portion 510 or the second end portion 520 for a furtherreduction in contactor parts and cost, and increased reliability.

FIG. 12 shows an embodiment of a contactor 600 of particular use inproviding ozonated liquids for semiconductor wet bench processing. Thecontactor 600 can be used independently of the ozonated water generator1000.

The contactor 600 includes a tubular portion comprising a housing 610made from a material that is compatible with semiconductor processing. Afluoropolymer is preferred, such as perfluoroalcoxy (PFA) to providecompatibility with the presence of hydrofluoric acid. A first end of thehousing 610 is joined in fluid communication with a first fitting 620.The first fitting is used for connection to a liquid supply line, forexample a DI water supply line or a sulfuric acid supply line. A secondend of the housing 610 is joined in fluid communication with a secondfitting 630. The second fitting is used for connection to an ozonatedliquid supply line. A third fitting 640 is joined in gaseouscommunication with a side of the housing 610 preferably nearer to thefirst fitting 620 than to the second fitting 630. The third fitting 640is used for connection to a gas supply line, the gas comprising ozone.The fittings 620, 630, 640 are made with use of semiconductor processingcompatible components, for example Flaretek® port connections availablefrom Entegris, Inc. (Chaska, Minn.).

The tubular portion further comprises one or more internal mixingelements 650, some of which are seen, in FIG. 12, in a cut away crosssection of the tubular portion. The elements 650 cause turbulence andmixing of gas that enters the housing 610 via the third fitting 640 andliquid that enters the housing 610 via the first fitting 620. Thismixing helps to provide a relatively high efficiency mass transfer ofozone diffusion into the liquid.

A variety of turbulence inducing shapes are suitable for the elements650. Curved shapes are preferred, with an extent along the length of thehousing 610 greater than an internal width of the housing 610. Aninternal width of the housing 610 is about 5 to 30 millimeters andpreferably 15 millimeters for typical semiconductor processingapplications.

In one embodiment, each of the elements 650 has upstream and downstreamends that are substantially flat and twisted relative to each other. Thesymmetry of the twist can alternate, for example from left-handed toright-handed corkscrews, from element 650 to element 650 along thehousing 610. In another embodiment, the symmetry alternates in groups ofelements 650. In another embodiment, the element 650 symmetry alternatesrandomly.

The contactor 600 has particular utility in supplying ozonated liquidsto semiconductor processing wet benches. FIG. 13a shows a typical priorart wet bench 1370. A liquid, such as deionized water or sulfuric acid,is delivered to the wet bench 1370 along a liquid delivery line 1320.Ozone is delivered separately to the wet bench 1370 via an ozonedelivery line 1310. Ozone bubbles 1340 are injected into liquid 1330 inthe wet bench 1370. As the ozone bubbles 1340 rise through the liquid1330, a portion of the ozone diffuses into the liquid, providing anozonated liquid for treatment of semiconductor wafers residing in thewet bench (not shown).

In contrast to prior art methods, a wet bench system is shown in FIG.13b. The contactor 600 receives ozone from a gas supply line 615 andliquid from a liquid supply line 612 and delivers ozonated liquid 680 toan ozonated liquid delivery line 660 for delivery to a wet bench 670.Though ozone bubbles 690 are present in the ozonated liquid 680, theturbulent mixing of liquid and ozone gas prior to delivery to the wetbench 670 has several advantages. The ozonated liquid 680 in the wetbench 670 has an ozone concentration that is more uniform and, ifdesired, greater than in prior art methods. Further, more efficient useis made of ozone gas. Existing wet bench systems of the prior art typecan be readily converted to the type shown in FIG. 13b, largely usingexisting plumbing.

Provision of ozonated DI water following the principles illustrated bythe embodiment of FIG. 13b has several advantages over use of ozonatedwater generators for supply to a wet bench 670. The embodiment of 13 bis far less expensive and far more reliable. Further, reduced downtimedue to a highly reliable ozonated DI water source reduces the very highcosts typically associated with shutdowns of a semiconductormanufacturing process line. Reduced repairs further add to the safety ofa manufacturing operation.

In the following, highly pure water, as typically used in semiconductorprocessing is variously referred to as DI water, water, pure water andultra-pure water (UPW).

FIGS. 14-16 illustrate embodiments of apparatus and methods to controlozonated water flow and concentration. FIG. 14 is block diagram of anembodiment of an ozonated water flow and concentration control unit1400. The unit 1400 receives ozonated water from an ozonated watergenerator and DI water from a DI water source. After mixing the receivedliquids, the unit 1400 delivers ozonated water of a modified ozoneconcentration and/or flow rate to one or more process tools.

The unit 1400 can include a DIO3 flow control valve 1410 and/or a DIwater flow control valve 1420. The valves 1410, 1420 can be used tocontrol the concentration of ozone in ozonated water exiting the unit1400 by controlling a mix volume ratio of ozonated water from thegenerator and water from the DI water source. The valves 1410, 1420 canalso be used to control the flow rate of output ozonated water.References to DI water are herein understood to encompass highly purewater as commonly used in semiconductor processing.

The control unit 1400 permits control of ozonated water concentrationand/or flow rate for one or more process tools while an ozonated watergenerator operates in a steady-state. As described below, use of one ormore units 1400 permits a single generator to supply two or more processtools each with a different concentration of ozonated water.

A “process tool” as used in the present description refers to any pieceof equipment, or portion of a piece of equipment, that utilizes ozonatedwater. For example, separate baths in a single piece of equipment can beseparate process tools.

FIG. 15 is a block diagram of an embodiment of multiple control units1400, an ozonated water generator 1000, a pure water source 20 and threeprocess tools 40A, 40B, 40C. The control units 1400 work in cooperationwith the ozonated water generator 1000 to separately control theparameters of ozonated water delivered to the process tools 40A, 40B,40C. Other embodiments include more or fewer process tools, and/oradditional generators 1000.

FIG. 16 is a block diagram of an embodiment of a generator 1000 and acontrol unit 1400 delivering ozonated water to two process tools 40D,40E. The generator 1000 delivers ozonated water directly to one of theprocess tools 40D, and thus directly controls the concentration of theozonated water that is delivered to the tool 40D. The control unit 1400controls the concentration of ozonated water delivered to the secondtool 40E.

Other embodiments vary the number of process tools, and vary the numberof the process tools that receive ozonated water via one or more controlunits 1400. Some embodiments include two or more generators 1000, forexample, to provide a greater quantity of ozonated water.

FIG. 17 is a detailed block diagram of another embodiment of a controlunit 1400A, which illustrates one detailed implementation. The controlunit 1400A includes: pneumatic control valves V1, V2; pneumatic shutoffvalves V4, V5; a manual adjust valve V3; a flow indicator F1; pressuresensors PR1, PR2; and flow sensors FR1, FR2. The pneumatic valves V1,V2, V4, V5 are operated using, for example, compressed dry air.

The control unit 1400A operates as follows. Desired tool process flowrate and ozone concentration are set via a control panel portion of thecontrol unit 1400A, or set remotely via computer control. The controlunit 1400A can receive, from an ozone generator, the value of theconcentration of incoming ozonated water.

Incoming ozonated water passes through a pneumatic shutoff valve V5, andhas its pressure and flow rate measured respectively by a pressuresensor PR1 and a flow sensor FR1. Similarly, incoming pure water passesthrough a pneumatic shutoff valve V2, and has its pressure and flow ratemeasured respectively by a pressure sensor PR2 and a flow sensor FR2.The two fluids are mixed after passing the flow sensors FR1, FR2, andthen pass through a pneumatic valve V1 to exit the control unit 1400A.

The control unit 1400A compares the selected ozone concentration withthe concentration of the incoming ozonated water, and responsivelyselects a required dilution ratio. The pneumatic valve V2 in the purewater line is adjusted, and the resulting flow rates obtained by theflow sensors FR1, FR2 are compared. Adjustments continue, via a closedloop process, until the flow rates provide the selected dilution ratio.

The control unit 1400A can also determine the total flow rate measuredby the flow sensors FR1, FR2, and compare the total to the selected flowrate for the output ozonated water. The pneumatic valve V1 near theoutput port can be adjusted via a closed loop until the selected outputflow rate is achieved.

The manual valve V3 permits, for example, adjustments to obtain adesired level of flow to a drain, as measured via the flow indicator F1.The flow to drain passes through one of the pneumatic shutoff valves V4.Monitoring of the pressure sensors PR1, PR2 can permit emergencyshutoff, if, for example, safe pressure levels are exceeded.

In one embodiment, the generator 1000 delivers ozonated water that issaturated with ozone and a control unit performs mixing under pressure,to avoid out-gassing of the ozone. In one embodiment, incoming saturatedozonated water passes through a straight input line of uniformdimension.

Features of the invention can provide numerous benefits, for example,rapid setting of concentration and flow rate which enables fast ramp upand ramp down of the process fluid (allowing optimized process cycles instop/go mode), and an enlarged flow and concentration performance rangeof a process fluid.

In illustrative embodiments, a control unit 1400 receives ozonated waterhaving a flow rate in a range of approximately 0 to 35 liters/min, andDI water having a flow rate in a range of approximately 0 to 42liters/min. A preferred drain flow is in a range of approximately 0 to 2liters/min. Ozone concentration in output ozonated water can be in arange of 0% to 100% of input ozonated water concentration. It is hereinunderstood that 0% ozone concentration in output ozonated water can beobtained by delivering only DI water to the output of a control unit.

While the invention has been particularly shown and described withreference to specific preferred embodiments, it should be understood bythose skilled in the art that various changes in form and detail may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims. For example, a control unitcan be used to control the flow and/or concentration parameters for twofluids other than ozonated water and/or DI water. For example, a controlunit can control the mixing of more than two fluids. For example, acontrol unit can include two or more outputs; each output can supplyozonated water having a different concentration.

What is claimed is:
 1. A ozonated water control unit comprising: anozonated water input port for receiving ozonated water having a firstconcentration from an ozonated water generator; a water input port forreceiving water from a source; an ozonated water output port in fluidcommunication with the ozonated water input port and the water inputport; a valve for controlling a flow rate of water in the water inputport to produce ozonated water having a second concentration in theoutput port, in cooperation with a flow rate of ozonated water in theozonated water input port a second ozonated water output port in fluidcommunication with the ozonated water input port and the water inputport, the second ozonated water output port for supplying ozonated waterhaving a third concentration.
 2. The ozonated water control unit ofclaim 1, further comprising a flow sensor for measuring the flow rate ofwater in the water input port, wherein the valve is adjusted in responseto the measured flow rate to obtain a selected flow rate to produce theozonated water having a second concentration.
 3. The ozonated watercontrol unit of claim 2, further comprising a flow sensor for measuringthe flow rate of the received ozonated water in the ozonated water inputport, and a valve for controlling a flow rate of the received ozonatedwater in the ozonated water input port, wherein the valve forcontrolling the flow rate of the received ozonated water is adjustedresponsively to the measured flow rate of the received ozonated water toprovide a selected ratio of the flow rate of the received ozonated waterto the flow rate of the received water from the source.
 4. The ozonatedwater control unit of claim 2, wherein the second concentration is in arange of 0% to 100% of the first concentration.
 5. A ozonated watersupply system, comprising: an ozonated water generator; a first ozonatedwater control unit in fluid communication with the ozonated watergenerator, the control unit comprising: an ozonated water input port forreceiving ozonated water having a first concentration from the ozonatedwater generator; a water input port for receiving water from a source;an ozonated water output port in fluid communication with the ozonatedwater input port and the water input port; and a valve for controlling aflow rate of water in the water input port to produce ozonated waterhaving a second concentration in the output port, in cooperation with aflow rate of ozonated water in the ozonated water input port, and asecond ozonated water control unit in fluid communication with theozonated water generator for supplying ozonated water having a thirdconcentration to a second process tool while supplying ozonated waterhaving the second concentration to a first process tool.